First Report of a Phytoplasma Associated with Cactus Witches’-Broom in Yunnan (China)

H. Cai*, H.R. Chen, F. Li, and B.H. Kong

The Key Laboratory for Plant Pathology of Yunnan Province, Yunnan Agricultural University, Kunming, China 650201

*c-hong2000@263.net

Accepted for publication 13/12/01

Sixteen samples from naturally infected cactus (Opuntia linguiformis D.Griffiths) with symptoms of witches’-broom were collected from 5 different sites in Yunnan Province. Symptoms were typified by the production of many young cladodia (the flat leaf like stem), closely bunched together on the old cladodium (Fig. 1).

Figure 1. Opuntia linguiformis naturally infected with witches’-broom

Diseased and healthy plants were tested by PCR amplification for phytoplasma-specific 16S rDNA. Total nucleic acid was extracted from young cladodia by the method of Ahrens & Seemuller (1992) and used as the template in a nested PCR reaction using primers R16mF2/R16mR1 and R16F2/R2 (Lee & Gundersen, 1998). A 1.2 kbp DNA fragment was amplified from 11 diseased plants but not from known healthy or symptomless plants. The 1.2 kbp DNA fragment was purified, cloned and sequenced and the sequence deposited in the EMBL Database (Accession No. AJ293216). Using a multiple alignment program (DNAMAN Version 4.0) the sequence showed a high similarity with members of the 16SrII group of phytoplasmas (Lee & Gundersen, 1998). The highest homologies were with 16S rDNA of faba bean phyllody phytoplasma (99.7%) (Accession No. X83432), a member of the 16Sr group, subgroup C, and a cactus witches’-broom phytoplasma found in Mexico (99.4%) (Genbank accession No. AF200718). This is the first report of a phytoplasma associated with a disease in cactus from Yunnan (China).

References

Ahrens U, Seemuller E, 1992. Detection of DNA of plant pathogenic mycoplasma-like organisms by a polymerase chain reaction that amplifies a sequence of the 16S rRNA gene. Phytopathology 82,828-832.

Lee IM, Gundersen-Rindal DE, Davis RE, Bartoszyk IM, 1998. Revised classification scheme of phytoplasma based on RFLP analysis of 16S rRNA and ribosomal protein gene sequences. International Journal of Systematic Bacteriology 48, 1153-1169.

The British Society for Plant Pathology